every gun is at least a bit unique, sorta like humans.
for the most part, the defacto touch hole diameter is .062" (1/16"). most offshore guns have slotted removable touch hole liners that are well under that diameter and it's more than worthwhile to get you a 1/16" drill bit and SLOWLY drill out the touch hole while it's still screwed in. you can drill it out fast if you slide down an appropriate size wood dowel, so you don't inadvertently punch through with too much force and drill the barrel innards. or just remove the liner and drill it. it will pay to use anti-seize lube (permatex, at all auto stores) on liner threads. in fact, use anti-seize grease on anything that screws into the barrel - this will pay big dividends years later.
keep the chamber CLEAN and DRY. the slightest bit of moisture will yield a pan flash or fizzled ignition. if you use a wet patch for fouling control you must follow with a dry patch or all bets are off.
compact your powder charge. this is particularly important as the chamber area gets built up with caked BP residue. what does "compact" mean? it means bouncing the ramrod to send a patched ball down the tube and properly seat it onto the chamber powder. this will insure that there is no air space 'tween the patched ball and the chamber powder. pounding on the ramrod may NOT insure there is no air space! the Best method is "bouncing the rod". flick the ramrod down on the patched ball - when the rod trampolines upwards, that is the indication that the patched ball is seated and the chamber powder has been properly compacted.
you MUST pick the touch hole after the barrel has been charged and before the pan is filled! pick DEEP into the touch hole. this does two really good things - (1) it increases the area (amount) of chamber powder that the ignited pan will heat up for ignition explosion, and (2) it insures that any touch hole crud gets pushed out of the way. a Great touch hole pick is a piece of ACOUSTIC guitar string, perhaps .040 to .056 gauge. acoustic strings have a steel core that is wrapped with phosphor bronze wire (non sparking) and that saw-like wrapping digs in well to the compacted chamber powder.
special attention MUST be given to guns with "patent breeches" - this means literally all offshore built guns. patent breeches mean that there's an ante-chamber behind the real chamber, and its narrow flue will not allow a bore sized cleaning rod to get in there and scrub out the BP residue. swap out the rod's jag for a small .22 to .38 brush draped with a cleaning patch to get into that ante-chamber, and don't forget a drying patch afterwards!
as to the flint itself, thin "fine" flints (with a single beveled cutting edge) are usually better than fat "common" flints (dual edged). TOTW will send fine flints if specified in yer order.
flintlock geometry is important for both consistent ignition and the life of the flint itself. finding the sweet spot for where the flint hits the hammer steel (frizzen) is important and may mean the flint will need to be in the cock jaws bevel down instead of up. at half cock the flint's edge should be very close to the hammer steel and aimed at least 2/3rds to 3/4ths up.
the difference between using null-B and 3f for pan charging ain't worth a hoot to be concerned about. finer powder WILL be more susceptible to air moisture than coarser powder, and that could mean no pan flash. back in the day, most powder was about 1f granulation, and today most folks are scrambling to pan charge with 4f - not needed and maybe should NOT be used! i use one powder for both tube and pan - 3f - don't matter what bore size, either. food for thought?
r.
PS - it helps to keep the pan, flint, and hammer steel clean 'tween loads, too.